This invention relates to a communication system, a terminating apparatus which is one of a station's terminal equipment and a subscriber's terminal unit of the communication system, and a PON (Passive Optical Network) virtualization method and, in particular, to virtualization in a PON.
FIG. 1 shows a typical network in an EPON (Ethernet® Passive Optical Network). The network includes ONUs (Optical Network Units: subscriber's terminal units) 4a to 4c which have Ethernet® ports 41a to 41c and PON ports 42a to 42c, respectively. The EPON (or GEPON (Gigabit Ethernet® Passive Optical Network)) is disclosed in Japanese Unexamined Patent Application Publications (JP-A) Nos. 2006-352350 and 2006-109500.
An OLT (Optical Line Terminal: station's terminal equipment) 6 has a plurality of Ethernet® ports 61 and 62 and a PON port 63. The PON ports 63 and 42a to 42c of the OLT 6 and the ONUs 4a to 4c are connected in a star topology via an optical coupler 5 by the use of optical fibers.
Generally, an EPON apparatus is produced in the form of a layer 2 switch or router having an Ethernet® port. Practically, the PON port, which physically is one port, is logically divided by LLIDs (Logical Link Identifiers) defined by IEEE (Institute of Electrical and Electronic Engineers) 802.3 (clause 65).
The LLIDs are in one-to-one correspondence to MAC (Media Access Control) addresses of the ONUs. Therefore, as the number of logical ports is increased, a corresponding number of MAC addresses are consumed. For example, for one ONU which supports 8 LLIDs, 8 MAC addresses are consumed. Therefore, depletion of the MAC addresses is a problem of deep concern.
In the above-mentioned related communication system, the LLIDs are used to construct a PON according to IEEE 802.3. The LLIDs are in one-to-one correspondence to the MAC addresses of the ONUs. Therefore, if the number of LLIDs for each ONU is increased, a large number of the MAC addresses are consumed.